NIS/TPO-modified H1299 cells markedly increased 125I uptake and retention. A, NIS- or both NIS/TPO-modified cell clones were categorized as >100×, 50–100×, 10–50×, 5–10×, 1–5×, and no increase based on 125I uptake levels. B, after incubation with 125I for 1 h, the medium containing radioiodide was removed at various time points (0–30 min). The cell-associated radioactivity was measured with a gamma counter and expressed as percentage of remaining radioactivity versus the original levels (time 0 min). Remaining radioactivity in all three NIS/TPOclones was significantly elevated compared with the NISclone (P < 0.05 at time points 5–30 min).

NIS/TPO-modified tumor xenografts show marked increase in 125I uptake in vivo. Three h after administration of 125I (1 μCi/mouse) by i.p. injection, tumors from each group (n = 8) of mice were removed, weighed, and the tumor-associated radioactivity was determined by a gamma counter. The results were expressed as the mean; bars, ±SD. ∗, P < 0.05; ∗∗, P < 0.01 compared with the controls.

Iodide induces an increase in ROS level and iodide-induced apoptosis is sensitive to N-acetylcysteine inhibition. The NIS/TPO-modified NSCLC cells were treated with variable concentration of KI (A, diluent only; B, 10 mm; C, 20 mm; D, 30 mm) for 24 h. Cells were then incubated with DCFH-DA for 1 h and analyzed by FACScan. The green peaks (A–D) show the background level of mean fluorescence in cells receiving diluent only. The purple peaks (A–D) demonstrate a progressive shift of mean fluorescence intensity to the high end in cells when KI supplement is increased. The purple peak overlaps the green peak when KI concentration is reduced to 5 mm (data not shown). E, the NIS/TPOmodified NSCLC cells were treated with variable concentration of KI (0–30 mm) in the absence or presence of N-acetylcysteine (5 mm) for 48 h. The culture medium from each sample was collected for NMP ELISA. ∗, P < 0.01; bars, ±SD.

Iodide-induced apoptosis is associated with overexpression of CDKN1Aand down-regulation of survivin. A, an increase in CDKN1Aproteins after incubation with 30 mm KI for 24 h was observed in three NIS/TPOclones tested by ELISA. B, ± a decrease in survivin proteins after incubation with 30 mm KI for 24 h was demonstrated by ELISA in two NIS/TPOclones tested. Control cultures received solvent only. The results are expressed as the mean; bars, ±SD. ∗, P < 0.05; ∗∗, P < 0.01 compared with the controls.